Controller for stopping motordriven machines



Nov. 29, 1949 c. P. FELDHAUSEN CONTROLLER FOR STOPPING MOTOR-DRIVEN MACHINES Filed June 26, 1947 2 Sheetg-Shet 1 O O O O 0O 00 IO w mwmm 5 D 4111 I 1 11 1111 1s Nov. 29, 1949 c. P. FELDHAUSEN CONTROLLER FOR STOPPING MOTORDRIVEN MACHINES 1 Filed June 26, 1947 2 Sheets-Sheet 2 m u 7 l g 5 s m m WDEL W. o: E ii ii M. m R1 5 Patented Nov. 29, 1949 UNITED CONTROLLER FOR STOPPING MOTOR- DRIVEN MACHINES Cyril P. Feldhausen, Wauwatosa, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application June 26, 1947, Serial No. 757,142

9 Claims. 1 This invention relates to controllers for stopping motor driven machines, controllers embodying the invention being especially advantageous for rotogravure presses.

Such presses are commonly equipped with ink removing knives rendering it important to insure against even a few degrees of reverse movement of the press in stopping. This necessitates terminating mechanical braking prior to bringing the press to zero speed because if this is not done some degree of backup of the press is likely to occur. Self-braking of the motor supplemented by mechanical braking is highly desirable and heretofore plugging supplemented by mechanical braking has been employed with some success,

dropping of the plugging relay having been utilized to energize the brake solenoid for release of the mechanical brake. However, such control has risk of power reversal of the motor and further to provide means in conjunction with the electrical braking means to efiect mechanical braking until the press closely approaches zero speed,

and then to function with reliability to effect release of the mechanical brake.

Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate certain embodiments of the invention which will now be described, it being understood that the embodiments illustrated are susceptible of modification without departing from the scope of the appended claims.

In the drawing, I Figure 1 shows schematically and diagrammatically a preferred embodiment of the invention, and

Figs. 2 and 3 illustrate diagrammatically certain of the possible modifications of the control of Fig. 1.

Referring to Fig. 1, the same shows a three phase alternating current slip ring motor M having a primary P and a secondary S.

The motor secondary has the usual delta coni nected resistors R, R and R to be excluded from motor terminal T to motor terminal T tacts and is of the normally closed type.

circuit in steps by triple pole electromagnetic switches A A A and A in the usual manner for speed control. Also the resistors are under the control of a triple pole electroresponsive switch T to provide increased torque of the motor in starting. For simplicity of illustration the showing of connections between the resistors and their control switches aforementioned has been confined to the connections for resistor R, it being understood that resistors R and R have similar connections to said control switches.

The primary P of the motor is adapted to be supplied from lines L L and L through a triple pole electromagnetic switch F for power operation, whereas the motor primary is adapted to be connected to lines L and L for dynamic braking. The connections for power operation which are established by the switch F are so well known and are so simple as to render description unnecessary. The switch B through its contacts l connects motor terminal T to line L and through its contacts 2 connects motor terminal T to line L whereas through its contacts 3 it connects Thus provision is made for dynamic braking of motor M in a well known manner for stopping of the motor. In practice the switches F and B are preferably mechanically interlocked in one of the well known ways to prevent closure of both at the same time which would provide a short-circuit across lines L and L However, the mechanical interlock has been omitted for simplicity of illustration.

For mechanical braking of the motor there is shown a brake B having an electromagnetic winding B to effect its release for free rotation of the motor, as is customary.

The controller shown for the aforementioned switches and brake releasing winding is largely of well known form comprising an inch push button switch ID, a run push button switch H, a stop push button switch l2, a brake relay BR, a relay ICE and the usual drum type controller D for selection of the switches A to A to be energized for speed regulation. The stop push button switch l2 comprises a single set of con- The push button switch I l is of the double throw type having normally bridged up contacts l5 and. normally unbridged down contacts IS. The inch push button switch which is of well known type comprises two movable contacts I1 and I8 re-- spectively to bridge stationary contacts is and 29. It is ineffective until pushed to bridge contacts 20, whereas it remains effective to continue inching after releasing contact it from contacts 29 so long as contact l? bridges contacts Further the control means illustrated comprises a relay 22 having a double ended pivoted contact arm 23 which in one position bridges contacts 24 and 25 and which in another position disengages said contacts. The arm 23 is designed to inherently retain either of such positions, and an electromagnet 25 when energized momentarily is adapted through the medium of its plunger to move arm 23 into bridging engagement withxcontacts 24 and 25. A second electromagnet 21 when energized and when unopposed is adapted through the medium of its plunger to rock the arm 23 out of engagement with contacts 24 and 25. Such action of electromagnet 21 is opposed by an electromagnet 28 which when energized to a predetermined degree effectively restrains the electro1nag net 21 against action. The electromagnet 26 is under the control of the run push button switch I, whie the electromagnet 21 is under the control of electroresponsive switch B, the restraining electromagnet 28 being under the control of. a

differential current transformer 29. The transformer 29 comprises windings 29 and 29 inwhich are induced currents by the currents in difierent branches of the dynamic braking connections established by switch B. This transformer is similar to that shown in the patent of E. Poll, No. 2,417,012, March 4, 1947, and functions during braking to maintain the electromag-net 28 eii'ective to prevent opening of relay 22 until the motor M closely approaches zero speed.

Further describing the controller of Fig. 1 and g throughout inching. Also the relay 22 remains idle during inching, there being no braking for stopping after inching.

More particularly, depression of the inch push .button switch l6 completes a circuit from line L through stop switch 12, normally closed contacts 30 of braking switch B, and contacts 2!! of switch ID, by conductor 3! to and through normally engaged contacts 52 of switch F, by conductor 33 through the winding of switch '1, by conductor 34 to line L ductor 3! by conductor 35 through the winding of switch F by conductors 36 and 3'! to conductor 34, and thenceto line L This provides for response of switches T and F for high torque starting, the contacts'32 of switch F having a time 918-! 1, ;ment in opening sufiicient to permit starting .of .themotor. ;in'a.ny ofthe well known ways and when Contacts Suchtime elemcntmay be afforded 32 disengage switch-T is dropped putforinclusion ofall secondary resistanceduring continued energization of switch F by push button'switch I0. .As soon as switch Fresponds its contact 39 engage to shunt the contacts 18 and 28 of push button switch [0 through the contacts I! and IQ of switch ID. This inching control is in accordance with well knownpractice.

When the run button II is depressed it establishes an energizing circuit for relay ICR which .in responding establishes a maintaining circuit .for itself. Also this relay in vresponding such.

Also circuit is completed from con-. 7;

gizes the switches T and F for starting the motor with relatively high torque and then including all of the secondary resistance through deenergization of switch T. Then upon release of push button switch H the ICE relay maintains switch F energized and said switch ll establishes a feed connection to'the drum ;D to energize such of the switches A to A as are selected by the drum for energization. As heretofore explained the wind- .ing B of the mechanical brake is normally energized for release of the brake and the brake re- ;mainsureleased pending stopping.

Relay lCR in addition to efiecting establish- ;ment of running connections as aforedescribed also establishes energizing connections for the electromagnet 26 of relay 22, causing the arm 23 of said relay to move into engagement with contacts 24 and 25. This operation of the relay 22 has no immediate results but prepares for stopping action of the controller.

More specifically operationof the run push button switch ll connects the winding of relay ICR to line L through thenormally closed contacts 30 of switch B and stop push button switch 12, whereas said windingis connected to line L by conductors 31 and 34. Relay l-CR upon responding engages its contacts 4t to parallel contacts 16 of push button switch H and engages its contacts 4! to establish a circuit paralleling the contacts 20 of inch switch It], thereby energizing switches T and F as described in detail hereinbefore. Also relay ICR completes circuit from line L through its contacts Auto and through the electromagnet 26 of relay 2?. to and through contacts 43 of switch T, by conductor 34 to line L opening of switch T thus effecting deenergization of electromagnet 26. The momentary energization of electromagnet 26 of relay 22 moves the arm 23 with a resulting tendency to energize the operating winding of brake switch B, but meanwhile relay ICR disengages its contacts 54 to defeat such tendency. The energizing circuit of the Winding of braking switch B. may be traced from line L through said winding and through contacts 44 of relay ICR by conductor 45, to and through the arm 23 of relay 22 by conductors 46 and 31 to conductor 34, and thence to line L Stopping of themotor is .eliected bydepressing the push button switch 12 which deenergizes the switch F to interrupt running connections and which also deenergizes relay lCR. Relay I CR in releasing engages its contacts 44 to complete the previously traced energizing circuit of the winding of switch'B. Switch B thus responds, disengaging its contacts .30 to render ineffective reclosure of stop switch l2, and engages its main contacts I, 2 and 3-130 establish dynamic braking connections for motor M. Moreover contacts 3 of switch B connect the winding of brake relay BR across lines L L said winding being convheated across thecontacts of onepole of switch Thus upon response of switch .B the brake relay BR is energized to disengageits contacts 41 which are in circuit with the normally energized winding of mechanical brake B This renders the mechanical brakeefiective to supplement the electrical braking.

Upon establishment of braking connections the differential current transformer 29 effects energization of the restraining electromagnet 28 of relay 22, energizing said electromagnet sufiiciently to prevent action of the electromagnet 21, which as will be apparent is in parallel with the winding of brake relay BB. for energization :upon response of braking switch 3; Dynamic braking and mechanical braking will continue 'until the current supplied to the electromagnet 28 by the differential current transformer drops a to a predetermined value, the transformer being result of deenergizing braking switch B, which in turn deenergizes brake relay BR along with the electromagnet 2'! of relay 22. Brake relay BR thus re-engages its contacts 41 to energize the releasing winding B of the mechanical brake substantially simultaneously with interruption of dynamic braking connections by deenergization of braking switch B. Thus the motor and the press or other machine driven thereby may come to rest without danger of power reversal or of backup as the result of mechanically braking to a standstill.

Referring to the modified controller of Figs. 2 and 3, it differs from that shown in Fig. 1 mainly in the means for controlling termination of braking and the means for controlling the primary connections of the motor.

Referring to Fig. 2, the motor primary connections are in this instance controlled by a twopole electromagnetic switch 5% and two single pole electromagnetic switches 51 and 52. The switches 50 and iii jointly control power connections for running, whereas the switches 50 and 52 jointly control dynamic braking connections, such power and dynamic braking connections being the same as in Fig. 1. The dynamic braking connections as in Fig. l have associated therewith a differential current transformer 53, but the transformer is employed in connection with a series relay SR in lieu of the relay 22 of Fig. 1. The motor in this instance is the same as in Fig. 1, and while for simplicity of illustration the control for the secondary circuit is not shown it may be assumed that such control is the same as that shown in Fig. 1.

Referring to Fig. 3, the controller shown therein comprises push button switches, a brake coil B a brake relay BR and a relay ICR like the corresponding elements of Fig. 1 except for the number of contacts with which the relays are provided. Also in this instance the controller comprises an additional electromagnetic relay ZCR.

In View of the fact that the relays similar to those of Fig. 1 differ in respect of contacts a new group of reference characters will be employed for the relay contacts to avoid confusion.

The controller of Fig. 3 provides for inching in a manner similar to that of the controller of Fig. 1 except that the two switches 50 and 5| must be energized to efiect completion of the power connections. The inch switch completes circuit from line L through the stop push button l2 and normally closed contacts 55 of relay BR,

through said switch switches T and 5! in parallel to line L l0 and the windings of Switch T in responding provides for short-circuiting of of push button switch ill by the contacts 19 of said switch I0, and switch 5| subject to a time element disengages its contacts 51 to deenergize switch T to reinsert the secondary resistance excluded for high torque starting. Release of the inch push button switch 10 stops the motor by deenergizing switches 50 and 5|.

Running is effected by the controller shown in Fig. 3 in a manner generally similar to that of the controller of Fig. 1, but in this instance both switches 50 and 5! must be energized for establishment of power connections as in inching. Depression of the run switch ll completes a circuit to line L for one terminal of the winding of relay ICR, through the contacts 55 of relay BR and stop push button switch [2, whereas the opposite terminal of the winding of relay lCR has a direct connection to line L Accordingly operation of the run switch H energizes relay [CR which through its contacts 59 parallels the inch push button switch, thereby effecting energization of switches T and 5| as aforedescribed, and energization of switch 5| effects energization of switch 50 as described in connection with inching operation. Also relay [CR through its contacts 6% establishes for itself a maintaining circuit, shunting the run push button switch to provide for continued operation after release of said switch. Assuming the motor secondary circuit to be provided with the control means shown in Fig. 1, release of the run push button switch I I would render effective the speed regulating means and the running connections would be maintained pending depression of the stop push button switch I2.

When the controller of Fig. 3 functions to establish running connections it also functions to effect circuit commutations preparatory to stopping. Thus relay ICR through its contacts 65 connects across lines L and L the winding of relay 20R and through its contacts 62 introduces a gap in the circuit of the winding of relay BR. Relay 20R being thus connected across lines L and L responds and through its contacts 53 closes a second gap in the energizing circuit of relay BR. Also relay 2GB through its contacts e4 partially completes a maintaining circuit for itself extending through contacts E5 of series relay SR and shunting the contacts SI of relay lCR. With the motor connected to lines L and L one winding of transformer 53 is excited and renders relay SR responsive for completion of the maintaining circuit just described. Furthermore relay 20R through its contacts 65 completes a maintaining circuit for the winding of switch by shunting the contacts 55 of switch 5|.

Thus when stop push button switch 82 is depressed it deenergizes relay ECR and switch ii to disconnect the motor from line L but relay ZCR and switch 58 remain energized, the series relay SR, being energized by the partially connected transformer 53. Consequently when relay lCR releases its contacts 62 connect one terminal of the winding of relay BR to line L through the contacts 63 of relay ECR and contacts of the series relay, and as the other terminal or" said winding is connected to line L relay BR responds. In responding relay BR through its contacts 51 connects across lines L and L the winding of switch 52, and switch 52 ipintly with switch completes the dynamic braking connections for the motor and renders effective both windings of the differential current transformer 53. Also relay BR in responding disengages its contacts to deenergize the brake coil B for setting of the mechanical brake. Thus the motor is, electrically and mechanically braked for stopping and as the motor approaches zero speed the series relay SR tends to release, the transformer being designed to effect release of the series when but only when the motor speed closely appioa' s zero value. When series relay SR releases energizes relay 203 which in turn releases i? and relay BR. Relay BR in turn releases switch 52 and again completes th energizing circuit of brake coil B thus provid both for interruption of dynamic braking connections and release of the mechanical brake.

What I claim as new and desire to secure by Letters Patent is:

1. In combination, aninduction motor, a mechanical brake therefor biased to set and having a releasing electromagnet, an alternating current supply circuit to which saidi'electromagnet is normally connected to release said brake, motor con nections inclusive of connections from said supply circuit which render said motor self-braking and inclusive of connecting and disconnecting means, means to deenergize said electromagnet to cause said mechanical brake to supplement selfbraking of said motor, and motor speed responsive means comprising 'a differential current transformer with windingsconnected in different portions of said motor self-braking connections, the last mentioned means operating under the iniiuence of said transformer to terminate self-oral:- ing and mechanical braking of said motor automaticall when but only when the speed of said motor is reduced to a value closely approaching zero.

2. In combination, an induction motor, a mechanical brake therefor tending to set having a releasing electromagnet, an alternating current supply circuit to which said electromagnet is normally connected to release said brake, means to establish selectively inching or running conne tions between said motor and said circuit, said means affording interruption of said connections, means responsive upon interruption by the former means of motor running connections, but not inching connections, to establish for self-braking of said motor connections including connections to said supply circuit, means controlling said releasing electromagnet to deenergize the same concurrently with establishment of said motor selfbraking connections, and means comprising a differential current transformer with windings connected in different portions of said motor selfbralring connections rendering the last mentioned means sensitive to motor speed variations to effect termination of self-braking of said motor and energization of said brake releasing electromagnet when but only when the speed of said motor is reduced to a value closely approaching zero.

3. In combination, a three phase induction motor, a mechanical brake therefor, a three phase alternating current supply circuit, means to establish dynamic braking connections for said motor comprising individual connections between a first and second terminal of said motor and two lines of said supply circuit and also comprising an interconnection between said second terminal of said motor and a third terminal of said motor, means controlling said mechanical brake for setting thereof concurrently with establishment of said dynamic braking connections and motor speed responsive means comprising a differential current transformer with windings in dnferent portions of the braking connections of said second and third terminals of said motor, the last mentioned means under the influence of said transformer operating to effect through the medium of the first and second mentioned means in terruption of said dynamic-braking connections and release of said mechanical brake upon decrease in the speed of .said motor when but only when the value of the motor speed closely approaches zero.

4. In combination, an induction motor, a mechanical brake therefor, an alternating current supply circuit, avmulti-pole switch to establish running connections between said motor and said supply circuit, a second multi-pole switch to establish dynamic braking connections for said motor including connections'between said motor and said supply circuit, control means for said switches to effect operation thereof selectively, means to release'said mechanical brake for motor operation and to efiect setting of said mechanical brake concurrently with establishment of dynamic braking connections by said second switch, and means comprising a differential current transformer with windings subjected to influence by current variations in different portions of said dynamic braking connections to render the last mentioned means sensitive to variations in speed of said motor as a function of change in difference of vector values of the currents resulting from change in motor speed, the last mentioned means effecting interruption of dynamic braking connections by said second switch and effecting through the medium of the second mentioned means release of said mechanical brake when but only when the value of the motor speed closely approaches zero.

5. In combination, a three-phase induction motor, a mechanical brake therefor, an alternating current supply circuit, a two-pole switch, two single pole switches, running connections between said motor and said supply circuit controlled by said two-pole switch and one of said single pole switches, dynamic braking connections for said motor controlled by said two-pole switch and the other of said single pole switches, control means for said switches to effect establishment of running connectionsancl dynamic braking connections selectively, means to release said mechanical brake for motor operation and to effect setting of said mechanical brake concurrently with establishment of said dynamic braking connections, and means comprising a differential current transformer with windings subjected to influence by current variations in different portions of said dynamic braking connections to render the last mentioned means sensitive to variations in speed of said motor as a function of change in difference of vector values of the currents resulting from change in motor speed, the last mentioned means eifectingthrough the medium of the aforementioned means interruption of said dynamic braking connections and release of said mechanical brake when but only when the value 0 the motor speed closely .-.approaches zero.

6. In combination, an induction motor, a mechanical brake therefor, an alternating current supply circuit, means to establish dynamic braking connections for said motor including connections fromsaid supply circuit, means controlling said mechanical brake to release the same for motor operation and to effect setting thereof upon establishment by the former means of dynamic braking connections, a differential current transformer with windings indifferent portions of the dynamic braking connections of said motor, and an electromagnetic .relay having control connec tions between the sameand said transformer and constituting with said transformer means sensitive to reduction in the motor speed to effect through the medium of the first and second mentioned means interruption of said dynamic braking connections and release of said mechanical brake when but only when the speed of the motor is reduced to a value closely approaching zero.

7. In combination, an induction motor, a mechanical brake therefor, an alternating current supply, circuit connections between said supply circuit and said motor for motor operation, said connections including means for completing and interrupting the same, dynamic braking connections for said motor including connections with said supply circuit and including circuit making and breaking means, means to release said mechanical brake for motor operation and to effect setting thereof concurrently with establishment of said dynamic braking connections, a relay operable to effect automatically through the medium of aforementioned means interruption of said dynamic braking connections and release of said mechanical brake, said relay having a first electromagnet to effect a given setting thereof which is responsive to the first mentioned means when establishing running connections, a second electromagnet for tripping which is energized by the second mentioned means upon establishing dynamic braking connections and a third electromagnet to delay tripping, and a differential current transformer to which said third electromagnet is connected, said transformer having windings connected in different portions of said dynamic braking connections and rendering said third electromagnet effective to delay tripping action until but only until the motor speed is reduced to a value closely approaching zero.

8. In combination, an induction motor, a mechanical brake therefor, an alternating current supply circuit, means to establish selectively inching or running connections between said motor and said supply circuit, said means affording interruption of said connections, means responsive upon interruption by the former means of motor running connections but not inching connections, to establish dynamic braking connections for said motor including connections between said motor and said supply circuit, means to release said mechanical brake and to maintain the same released for running and inching of the motor but effecting setting of said mechanical brake upon establishment of dynamic braking connections, a differential current transformer having windings in different portions of said dynamic braking connections and a relay under the influence of said transformer and constituting therewith means to effect interruption of said dynamic braking connections and release of said mechanical brake, said relay having a first electromagnet for setting thereof which is responsive to the first mentioned means when establishing running connections but not when establishing inching connections, a second electromagnet for tripping which is energized by the second mentioned means upon establishing dynamic braking connections and a third electromagnet to delay tripping, said third electromagnet being supplied with current from said transformer and under the influence of said transformer delaying tripping of said relay until but only until the motor speed is reduced to a value closely approaching zero.

9. In combination, an induction motor, a mechanical brake therefor, an alternating current supply circuit, means to connect said motor to said supply circuit for inching or running selectively and to interrupt said connections, means under the control of the former means to establish upon interruption of running connections but not upon interruption of inching connections dynamic braking connections for said motor in" cluding connections between said motor and said supply circuit, means to release said mechanical brake for running and inching of the motor and to set said mechanical brake concurrently with establishment of dynamic braking connections, a differential current transformer having windings connected in different portions of said dynamic braking connections to be sensitive to variations in speed of said motor, and a relay having an operating winding supplied by said transformer for response of said relay subject to release when but only when the motor speed is reduced to a value closely approaching zero, said relay when so released eiiecting interruption of said dynamic braking connections and release of said mechanical brake.

CYRIL P. FELDHAUSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 729,640 McCurdy June 2, 1903 1,113,593 Wright Oct. 13, 1914 2,409,264 Feldhausen Oct. 15, 1946 

